Evidence for dislocations or related defects present in CdTe and Cd1-xZnxTe crystals

Thermoelectric Effect Spectroscopy and Thermally Stimulated Current measurements were used to investigate trapping levels in semi-insulating CdTe and Cd1-xZnxTe crystals from multiple ingots grown by vertical Bridgman with over pressure control and high-pressure Bridgman methods. The crystals from different growth methods have different dislocation densities as well as Zn concentrations. The thermal ionization energies of these levels were extracted using both the variable heating rate and initial rise methods; the trapping cross sections were then calculated using the temperature maximum method. We report here that the shallow levels observed at E-1=0.11 +/- 0.02 and E-2=0.17 +/- 0.02 eV are intrinsic and the latter level is most likely related to the dislocation density.